Process of forming pyroxylin bodies.



" FREDERICK KNIFFEN, OF WILMINGTON,Y DEL. B.WA BE,

NEMOURS rownnn COMPANY, or w1LMmeroN, -nnLawnnE;. A conronnrronol.

NEW JERSEY 1,135,026. No Drawing.

To all whomit may concern Be it known/that I, FREDERICK KN FFEN,

of Wilmington, in the county of New Castle, and in the State ofDelaware, have invented a certain new and useful Improvement inProcesses of Forming Pyroxy'lin Bodies, and do hereby declare that thefollowing is a full, clear, and exact description thereof. a

The object of my invention has been to provide a process of formingpyroxylin bodies, by using a pyroxylin solvent having among others, thequalities of being cheap, of high solvent power, of being free fromprecipitation of pyroxylin,non-hygroscopic, and of'pleasant odor, and tosuch'ends my invention consists in the process of forming pyroxylinbodies, using the pyroxylin sol.- vent hereinafter specified. In thepyroxylin industries, such as in the manufacture of lacquers, artificialleather, varnishes, etc., there is a demand for a solvent having theabove stated qualities. None of the ordinary pyroxylin solvents, such asglacial acetic acid, amyl, acetate, wood alcohol, acetone with itshomologues and derivatives, is perfect in all-these properties, except,perhaps amyl acetate, and as to this latter solvent, its price isprohibitive. In each of these industries, it is desirable to have therelative proportions of the solvent and pyroxylin vary to get a solutionof a given strength, according to the nature of the film to be formed bydepositing the pyroxylin.

For instance, in lacquer work, the solution should not contain over fiveounces of pyroxylin per gallon in order-that a film of proper thicknessmay be deposited. 'In some of the decorative arts, a very heavy film isemployed which could be deposited from a solution containing as high astwenty 'ounces of pyroxylin per gallon. There is thus for each industrya strength of solution which is best adapted thereto. Where a solutionis desired having less pyroxylin than the total amount which the solventis capable of taking up (for instance, if a. solutionof twenty ounces ofpyroxylin to a gallon of solvent were desired, which is less than thetotal amount which the solvent.

would take up), it is unnecessary to have the entire gallon of solutioncomposed ofpure solvent, it only being necessary to have enough solventpresent to dissolvethe desired amount of pyroxylin. For economy,therefore, it is customary to add cheap, dil

Specification of Letters Iatent. Application filed April 12, 1918.Serial No. 760,573. L

I rnocnss or ro'nmms rrnoxnmisomnsf Patented Apr. 13, 1915.

assrqnon cm I}. I. no ron'r m:

uents v to. the solvent, which diluents are either entirely hop-solventor nearly so. The use of, diluents, however, introduces difliculties,among which may be mentioned the following: When, as used in a factory,

thesesolvents are evaporated contact with the ordinary room atmosphere(in-order to deposit, a; tihn of pyroxylin), there'is a. tendency,except as to amyl acetate, toward; a separation out of thenitrocellulose on other solvents through absorption of mois;

' ture from the air or through the change in the composition of thesolvent mixture 1' 7- sulting fromthe unequal rate of evaporation of itscomponents, this precipitation being usually evidenced bythe appearanceof a. whittish' substance, technically known as ration tends to decreasethe strength of the film and, insomecases, the whiteappearance producesobjectionable color effects.

I I have discovered that by using ethylacetate as the solvent and benzolas the diluent (with or without other components), a mixture is obtainedwhich has va; maximum solvent power and is'free from precipitation ofthe pyroxylin. Such mixture is also comparatively non-hygroscopic. IWhen these two material'sare mixed together, the reduction. in solventpower of the active principle ethylacetate, is so far resisted that themixture may contain ,as high as seventy percent, or even higher, ofbenzol. I find that during evaporation under ordinary factoryconditions, the ethylacetate. and benzol mixture deposits a film whichis'strong and transparent. I find that a solution containing about eightounces of pyroxylin and equal parts of ethylacetate and benzol, issuitable for most general applications, and except where the humidityand temperature are blushing or blooming or by the settling to thebottom ofa jellylikemass. Such sepastitute a normal solvent of readygeneral applicability, but the relative percentages of these ingredientsmay vary widely according to the conditions covering the innumerableuses to which the solution maybe put. I have given specific instancesmerely by way of illustration, and am not to be confined to theparticular proportions given, as they are to be regarded as typicalonly. An increase inthebenzol component results in reduced a cost, andits disadvantage lies. 1n the less rapid solvent action which such amixture would possess. Numerous other substances, such as. oils,-p1gments, gums, resins, etc., may be added to the pyroxyhn mixture,

each having its own properties, and these properties will, of course,affect the properties of the final mixture but the general I principle.will still obtain.

As the boiling points of the ethylacetate and benzol are in the sameneighborhood, it is not necessary to raise the temperatureof either muchabove the other in order to secure evaporation of the solvent portion ofl the solution. This possesses the advantage an apparatus, and one whichis usually large,

and there is a tendency for the vapor to es-' cape from the apparatus ifthe vapor tension is at all high.

I find that my mixture "is comparatively non-hygroscopic, which-is avery desirable quality, sincethe absorption ot water in such a solutionresults ina precipitation of the pyroxylin.

I claim: l

The process of forming a body of pyroxylin, comprising dissolvingpyroxylin in a mixture of ethylacetate and benzol, and

then causing the said mixture to evaporate. In testimony that I claimthe foregoing I have hereunto set my hand.

FREDERICK KNIFFEN.

Witnesses:

P. E. STRICKLAND, J. E. EMMONS.

